The present invention relates to a high speed predictive encoding and decoding system for frequency band compression of television video signals.
A television video signal produced through the horizontal and vertical scanning of an optical image has a high degree of correlation between neighboring scanning lines, neighboring picture elements and successive frames. To reduce the amount of information to be transmitted for frequency band compression, the so-called predictive encoding system has been proposed. One example of the predictive encoding system is of the intraframe type, in which the correlation is taken between the neighboring scanning lines or neighboring picture elements by subtracting from the present video signal level a predicted signal level corresponding to the level taken one scanning period or one picture element period earlier. Another example is of the interframe type, in which the predicted signal level corresponds to the level taken one frame period earlier.
For the details of the intraframe and interframe predictive encoding system, reference is made to the articles by Connor et al. entitled "Intraframe Coding for Picture Transmission", and Haskell et al. "Interframe Coding for Videotelephone Pictures", Proceedings of the IEEE, Vol. 60, No. 7, July 1972, pp. 779 to 799 (Literature 1).
A more sophisticated version of the predective encoding system based on the combination of the intraframe and interframe predictive encoding system has been proposed in the U.S. patent application Ser. No. 844,857 filed on Oct. 25, 1977, and assigned to the assignee of this application.
However, these conventional systems require high speed logic and memory circuits, because the subtraction of the digitized prediction signal from the incoming encoded video signal, and the quantization of the result of subtraction must be completed in one video sampling period, e.g., 10.sup.-7 second. This tends to make the system as a whole very costly to manufacture.